Sr and Nd isotopic systematics in ALHA 77005: Age of shock metamorphism in shergottites and magmatic differentiation on Mars

Journal Article · Fri Sep 01 00:00:00 EDT 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90363-3· OSTI ID:7266127

Jagoutz, E ^[1]

---

1. Max-Planck-Institut fur Chemie, Mainz (West Germany)

The meteorite ALHA 77005 belongs to the group of SNC meteorites which are thought to be fragments of the planet Mars. New Sr and Nd isotopic data are reported for ALHA 77005 whole rock and petrographically distinct mineral separates. Plagioclase crystallized from a plagioclase shock melt, fractionating the Rb/Sr ratio at the time of the shock event. A Rb/Sr age of 15 {plus minus} 15 Ma for the shock event is measured using this Rb/Sr fractionation. This shock age is, within error, identical to the exposure age of 2.5 Ma. Using augite and pigeonite a Rb/Sr crystallization age of 154 {plus minus} 6 Ma is measured, which is identical to the crystallization age of the Shergotty mesostasis-plagioclase. Petrographic evidence indicates that the cumulus olivine in ALHA 77005 is derived from a different source than the intercumulus liquid which crystallized the pyroxenes and the plagioclases. Petrographic comparison of all SNC meteorites suggests that most SNC meteorites are orthocumulates in which the cumulus phase comes from a different source than the intercumulus liquid. The interrelation of the different isotopic systems indicates that the SNC meteorites can be explained by mixing three isotopically distinct sources. These three sources were differentiated early in Martian history. In contrast to the Moon, where plagioclase fractionation is the dominant magmatic process, the major magmatic processes on Mars are mafic magmatism and mixing.

• OSTI ID: 7266127
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Vol. 53:9; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
FELDSPARS
CRYSTALLIZATION
ISOTOPE RATIO
METEORITES
ISOTOPE DATING
MINERALOGY
PETROGRAPHY
CHEMICAL COMPOSITION
GEOCHEMISTRY
GEOLOGIC HISTORY
IMPACT SHOCK
MAGMA
MAGMATISM
MARS PLANET
METAMORPHISM
NEODYMIUM ISOTOPES
OLIVINE
PYROXENES
RUBIDIUM ISOTOPES
STRONTIUM ISOTOPES
AGE ESTIMATION
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
ALKALINE EARTH METAL COMPOUNDS
CHEMISTRY
IRON COMPOUNDS
IRON SILICATES
ISOTOPES
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
MINERALS
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PLANETS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
580000* - Geosciences